This invention concerns a process for the adhesive metallization of ceramic materials by roughening of the materials and subsequent chemical metallization.
It is known that for the purpose of metallization of non-conducting objects, to use processes for chemical metallization. In order to obtain sufficiently greater adhesiveness it is necessary to roughen the surfaces of these objects mechanically or chemically. This is performed with plastics mainly by acid oxidative digestion of the surface.
In the field of electrical engineering, particularly in the electronics sector, ceramic materials such as aluminum oxide, berryllium oxide, ferrite, barium titanate as well as quartz or borosilicate have been employed for a long time. The surface of these objects, to which also enamel can belong, cannot be roughened in conventional manner, since they are not accessible to an oxidative attack.
A known process for the roughening of aluminum oxide ceramics is, for example, the treatment of such objects in melts of alkali hydroxides. By placing the objects in such melts, the surface can be sufficiently dissolved and thereby roughened, so that after appropriate activation through seeding with metal ions, an adhesive chemical metallization is possible.
It is a disadvantage with this process that upon extracting the object from the melt, very much alkali hydroxide gets carried off. The result is that, with the exception of platinum, this aggressive melt strongly attacks all known crucible materials. Moreover, during operation the melt becomes more and more enriched with the aluminum dissolved off from the surface of the ceramic material which leads to an increase in the melting point and therewith to necessarily higher energy supply.